Partial support for a special facility for ambulatory clinical investigation through The Johns Hopkins Out-patient General Clinical Research Center has been awarded through the Division of Research Resources for the past seven years. The accompanying proposal seeks support for a core facility for the provision of histocompatibility antigen testing in large groups of patients currently under investigation with chronic, familially occurring illnesses for the assessment of association between genetically determined human leukocyte antigen (HLA) specificities and appearance, persistence, and outcome of these diseases. Known associations requiring further evaluation include relationships between HLABw27 and the various types of Reiter's syndrome and between HLABw35 and hepatitis B surface antigenemia. New histocompatibility (HLA) disease associations to be sought involve patients with medullary thyroid carcinoma, familial polyposis coli, familial cryoglobulinemia, renovascular disease, polycystic kidney disease, and Chlamydial urethritis.